With the prosperous growth of electrical products consumption, the current trend of consumers' demand, including increased portability, computing power, memory capacity and energy efficiency, is for the dimension of such products to almost always be toward small size and delicate design.
The continual reduction in feature sizes results in greater demands on the techniques used to form the features. For example, photolithography is commonly used to pattern these features. Because lithography is typically accomplished by projecting light or radiation onto a surface, the ultimate resolution of a particular lithographic technique depends upon factors such as optics and light or radiation wavelength. However, the present optical lithography technique is inapplicable due to the inherent limitation of the optical characteristics.
A relatively new non-lithography patterning technique, called directed self-assembly (DSA), forms mask patterns through the self-assembly ability of block copolymers. Block copolymers are formed of two or more chemically distinct blocks. Generally, self-assembly is based upon the affinity or preference of one of the blocks for the underlying surface and/or air interface. Therefore, local variations in the surface polarity of the layer to which the DSA material is applied dictate how the block copolymers will align. DSA may be particularly useful for line/space frequency multiplication techniques.
While self-organizing materials may be used to form relatively small mask features, further decreases in the sizes of the mask features are desired due to the constant miniaturization of integrated circuits. Accordingly, there is a continuing need for high resolution methods to pattern small features.